Ultraviolet, on Channel 4 (UK)
Channel 4; IMDb; Templeton Gate; TV Tropes; Wikipedia
streaming sites: Amazon

Hmmm... Well, this was interesting. I don't remember it well, though. It was about like some government group or whatever, hunting vampires (except they weren't called vampires). It was all very modern, and had some kind of scientific (rather than supernatural) explanation for what the creatures were. And um... anyway, the agency used ultraviolet weapons against them.

I wish I could tell you more, but I can't. Sorry. Except, don't confuse it with the theatrical movie of the same name (which I still haven't seen). Oh, and I should say that I originally had this on my miniseries page, because it aired as such in the U.S. (on the Sci-Fi Channel). But it's actually a 6-episode limited series. Anyway, I really want to see it again, someday, at which point I should write a better review.